As part of the ongoing evolution of wireless communications systems, the enhanced dedicated channel (E-DCH) in CELL_FACH state feature was introduced into wireless standard specifications, such as the third generation partnership project (3GPP) Release 8 specifications. Wireless transmit/receive units (WTRUs) operating in a CELL_FACH or IDLE mode may use a contention based E-DCH channel for uplink (UL) transmission rather than a traditional random access channel (RACH). The contention-based E-DCH channel allows for WTRUs to transfer signaling and data at significantly higher data rates and for longer durations, which reduces transfer and state transition delays with an aim to provide a user experience that is closer to “always-on connectivity.”
Support for multiple transmission time interval (TTI) settings, (e.g., 2 ms and 10 ms), are allowed for the E-DCH in the CELL_FACH state. A single TTI setting, which may be determined and broadcast by the network, for example the universal mobile telecommunications system (UMTS) terrestrial radio access network (UT-RAN), may be used by all WTRUs accessing the E-DCH in the CELL_FACH state within a particular cell. While a smaller TTI, such as the 2 ms TTI, may be more advantageous from scheduling and latency standpoints, a larger TTI, such as the 10 ms TTI, may allow for a larger coverage area. Accordingly, the 10 ms TTI setting is often used throughout larger cells to allow for WTRUs, including those located near the cell edge, to reliably transfer signaling and data to the network.
Although the 10 ms TTI setting is used in some cases to ensure service reliability throughout the cell, it may desirable to take advantage of the fast scheduling and lower latency benefits of the 2 ms TTI. A number of methods to extend the coverage provided by the 2 ms TTI for E-DCH transmission in CELL_FACH have been proposed, such as TTI bundling. The application of TTI bundling for UL transmission using the E-DCH in CELL_FACH state may be used to improve the coverage with a smaller TTI, such as 2 ms TTI. However, a number of issues may need to be addressed. For example, it may need to be determined whether or not to apply TTI bundling. In addition, the automatic retransmission of the TTI bundling uses a lot of power perhaps unnecessarily which lowers the standby time and operating time of the User Equipment.
A method and an apparatus and a software product are thus needed to allow for more energy conservative use of the E-DCH channel.